Field of the Invention
The present invention relates to a sheet conveyance device and to an image forming apparatus, such as a copier, a multifunction peripheral (MFP), and a facsimile machine, including the same.
Description of the Related Art
A sheet conveyance device includes: a pair of separable contact rollers for conveying a sheet; a contact/separation mechanism that supports the pair of separable contact rollers in such a manner that the pair of separable contact rollers are able to come into separable contact with each other; and a solenoid that operates the contact/separation mechanism. The sheet conveyance device drives the solenoid so that the contact/separation mechanism causes the pair of separable contact rollers to come into pressure contact with each other, and cancels the driving of the solenoid so that the contact/separation mechanism causes the pair of separable contact rollers to be separated from each other.
For example, the sheet conveyance device further includes a document moving reading structure that reads a document image while moving a document as the sheet. In this configuration, the pair of separable contact rollers are components of the document moving reading structure, and are disposed more on a downstream side than a reading position for the document, in a conveyance direction of the document.
Such a sheet conveyance device conveys a plurality of the sheets one by one at an interval based on the following rule to prevent the temperature rise of the solenoid that has been energized. Specifically, the solenoid is driven only in a period during which the pair of separable contact rollers are to be in pressure contact with each other (for example, a sheet passing period during which the sheets pass through the pair of separable contact rollers) (a pressure-contact period), and is not driven in the other (for example, an inter-document non-passing period between conveyance operations respectively for two consecutive documents to be conveyed by the pair of separable contact rollers) (a non-pressure-contact period).
In other words, in this conventional control configuration, a plurality of the sheets have been conveyed one by one at an interval with a solenoid driving operation and a solenoid driving cancel operation repeatedly performed. The solenoid driving operation is an operation of driving the solenoid to put the pair of separable contact rollers in a pressure-contact state, and is performed in the pressure-contact period in which the pair of separable contact rollers are to be in pressure contact with each other in the sheet passing period. The solenoid driving cancel operation is an operation of canceling the driving of the solenoid to put the pair of separable contact rollers in a separated state, and is performed in the non-pressure-contact period other than the pressure-contact period.
The conventional control configuration, in which the plurality of the sheets have been conveyed one by one at an interval with the solenoid driving operation and the solenoid driving cancel operation repeatedly performed, has the following disadvantage. More specifically, the operations of putting the pair of separable contact rollers in the pressure-contact state and to the separated state are repeated every time a sheet passes. Thus, the solenoid driving operations and the solenoid driving cancel operations are repeated, causing intermittent operating noise of the solenoid (more specifically, the operating noise of the pair of separable contact rollers), which can make a user irritated.
Japanese Unexamined Patent Application Publication No. 2004-123354 describes a technique related to the present invention. More specifically, Japanese Unexamined Patent Application Publication No. 2004-123354 describes a sheet conveyance device including a document moving reading structure that reads a document image while moving a document as the sheet. The document moving reading structure includes a pair of separable contact rollers disposed more on the downstream side than a reading position for the document in a conveyance direction of the document. In this configuration, a first pulse driving of a solenoid starts before the trailing edge of the document passes through the reading position, and then a second pulse driving of the solenoid starts after the trailing edge of the document has passed through the reading position.
The sheet conveyance device described in Japanese Unexamined Patent Application Publication No. 2004-123354 has no countermeasure against the temperature rise of the solenoid that has been energized and against the generation of the intermittent operating noise of the solenoid due to the solenoid driving operation and the solenoid driving cancel operation repeated.
All things considered, an object of the present invention is to provide a sheet conveyance device that can prevent the temperature rise of the solenoid that has been energized, and also can prevent the intermittent operating noise of the solenoid from being generated due to the solenoid driving operation and the solenoid driving cancel operation repeated, and thus can effectively overcome the disadvantage that the operating noise of the solenoid can make the user irritated, and to provide an image forming apparatus including the sheet conveyance device.